Hundreds of police, firefighters, paramedics and even utility workers have been trained and recently dispatched as “Terrorism Liaison Officers” in Colorado and a handful of other states to hunt for “suspicious activity” — and are reporting their findings into secret government databases.

It’s a tactic intended to feed better data into terrorism early-warning systems and uncover intelligence that could help fight anti-U.S. forces. But the vague nature of the TLOs’ mission, and their focus on reporting both legal and illegal activity, has generated objections from privacy advocates and civil libertarians.

“Suspicious activity” is broadly defined in TLO training as behavior that could lead to terrorism: taking photos of no apparent aesthetic value, making measurements or notes, espousing extremist beliefs or conversing in code, according to a draft Department of Justice/Major Cities Chiefs Association document.

All this is anathema to opponents of domestic surveillance.

Yet U.S. intelligence and homeland security officials say they support the widening use of TLOs — state-run under federal agreements — as part of a necessary integrated network for preventing attacks.